Engineering Entangled Coherent States of Magnons and Phonons via a Transmon Qubit

We propose a scheme for generating and controlling entangled coherent states (ECS) of magnons, i.e. the quanta of the collective spin excitations in magnetic systems, or phonons in mechanical resonators. The proposed hybrid circuit architecture comprises a superconducting transmon qubit coupled to a pair of magnonic Yttrium Iron Garnet (YIG) spherical resonators or mechanical beam resonators via flux-mediated interactions. Specifically, the coupling results from the magnetic/mechanical quantum fluctuations modulating the qubit inductor, formed by a superconducting quantum interference device (SQUID). We show that the resulting radiation-pressure interaction of the qubit with each mode, can be employed to generate maximally-entangled states of magnons or phonons. In addition, we numerically demonstrate a protocol for the preparation of magnonic and mechanical Bell states with high fidelity including realistic dissipation mechanisms. Furthermore, we have devised a scheme for reading out the prepared states using standard qubit control and resonator field displacements. Our work demonstrates an alternative platform for quantum information using ECS in hybrid magnonic and mechanical quantum networks

Demonstration of Weak-Link Physics in the Dynamical Response of Transition-Edge Sensors

We theoretically predict and experimentally observe the onset of weak-link physics in the dynamical response of transition edge sensors (TES). We develop a theoretical framework based on a Fokker-Planck description that unifies the TES electrical response, stemming from Josephson phenomena, with electrothermal effects due to coupling to a thermal bath. Our measurements of a varying dynamic resistance are in excellent agreement with our theory, thereby ruling out predictions based on a two-fluid model and establishing weak-link phenomena as the main mechanism underlying the operation of TES. Furthermore, our description enables the calculation of power spectral densities, paving the way for a more thorough investigation of the unexplained "excess noise" in long diffusive junctions and TES reported in recent experiments

Tuneable hopping and nonlinear cross-Kerr interactions in a high-coherence superconducting circuit

© 2018, The Author(s). Analog quantum simulations offer rich opportunities for exploring complex quantum systems and phenomena through the use of specially engineered, well-controlled quantum systems. A critical element, increasing the scope and flexibility of such experimental platforms, is the ability to access and tune in situ different interaction regimes. Here, we present a superconducting circuit building block of two highly coherent transmons featuring in situ tuneable photon hopping and nonlinear cross-Kerr couplings. The interactions are mediated via a nonlinear coupler, consisting of a large capacitor in parallel with a tuneable superconducting quantum interference device (SQUID). We demonstrate the working principle by experimentally characterising the system in the single-excitation and two-excitation manifolds, and derive a full theoretical model that accurately describes our measurements. Both qubits have high coherence properties, with typical relaxation times in the range of 15 to 40 μs at all bias points of the coupler. Our device could be used as a scalable building block in analog quantum simulators of extended Bose-Hubbard and Heisenberg XXZ models, and may also have applications in quantum computing such as realising fast two-qubit gates and perfect state transfer protocols

Combustion of HAN-based liquid monopropellants near the thermodynamic critical point

The high-pressure combustion properties of liquid monopropellants involving mixtures of hydroxyl ammonium nitrate (HAN), triethanol ammonium nitrate (TEAN), and water are considered theoretically. Liquid surface properties and the critical combustion pressure (the pressure required for the propellant surface to exceed its thermodynamic critical point) were found allowing for real-gas phenomena and the presence of dissolved combustion product gases in the liquid. Critical combustion pressures for the HAN-based monopropellants were found to be unusually high, ca. 2500 atm, with an estimated uncertainty of 50%. Predictions were unusually sensitive to the critical temperature of TEAN and the binary interaction parameter between TEAN and water; both must be known more accurately for definitive estimates of the liquid-surface properties of HAN-based monopropellants at high pressures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27077/1/0000068.pd

Stochastic aspects of turbulent combustion processes

Methods of using stochastic simulations to treat nonlinear interactions in turbulent combustion processes are described -- emphasizing the use of statistical time-series techniques to analyze the turbulence--radiation interactions of nonpremixed flames. Three aspects of the problem are considered, as follows: the statistics of scalar properties in turbulent flames, the formulation of algorithms to stimulate flame radiation based on flame statistics, and evaluation of the methodology using recent measurements for nonluminous flames. It is shown that the process becomes tractable through the laminar flamelet approximation whereby all scalar properties are taken to be solely functions of a conserved scalar like the mixture fraction. Thus, the simulations are designed to generate realizations of mixtures fractions along radiations path with the radiation properties of each realization found using a narrow-bond radiation model. An autoregressive process that reproduces probability density functions and spatial and temporal correlations of mixture fraction was found to yield reasonably good predictions of the statistical properties of spectral radiation intensities measured for turbulent carbon monoxide and hydrogen jet flames burning in still air. Although the approach appears to be promising, additional development is needed in order to treat some of the unique statistical features of turbulence that are not encountered during conventional use of statistical time-series techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29477/1/0000563.pd

Ballistic transport and boundary resistances in inhomogeneous quantum spin chains

Transport phenomena are central to physics, and transport in the many-body and fully-quantum regime is attracting an increasing amount of attention. It has been recently revealed that some quantum spin chains support ballistic transport of excitations at all energies. However, when joining two semi-infinite ballistic parts, such as the XX and XXZ spin-1/2 models, our understanding suddenly becomes less established. Employing a matrix-product-state ansatz of the wavefunction, we study the relaxation dynamics in this latter case. Here we show that it takes place inside a light cone, within which two qualitatively different regions coexist: an inner one with a strong tendency towards thermalization, and an outer one supporting ballistic transport. We comment on the possibility that even at infinite time the system supports stationary currents and displays a non-zero Kapitza boundary resistance. Our study paves the way to the analysis of the interplay between transport, integrability, and local defects

Measuring the burden of herpes zoster and post herpetic neuralgia within primary care in rural Crete, Greece

<p>Abstract</p> <p>Background</p> <p>Research has indicated that general practitioners (GPs) have good clinical judgment in regards to diagnosing and managing herpes zoster (HZ) within clinical practice in a country with limited resources for primary care and general practice. The objective of the current study was to assess the burden of HZ and post herpetic neuralgia (PHN) within rural general practices in Crete, Greece.</p> <p>Methods</p> <p>The current study took place within a rural setting in Crete, Greece during the period of November 2007 to November 2009 within the catchment area in which the Cretan Rural Practice-based Research Network is operating. In total 19 GP's from 14 health care units in rural Crete were invited to participate, covering a total turnover patient population of approximately 25, 000 subjects. For the purpose of this study an electronic record database was constructed and used as the main tool for monitoring HZ and PHN incidence. Stress related data was also collected with the use of the Short Anxiety Screening Test (SAST).</p> <p>Results</p> <p>The crude incidence rate of HZ was 1.4/1000 patients/year throughout the entire network of health centers and satellite practices, while among satellite practices alone it was calculated at 1.3/1000 patients/year. Additionally, the standardised incidence density within satellite practices was calculated at 1.6/1000 patients/year. In regards to the stress associated with HZ and PHN, the latter were found to have lower levels of anxiety, as assessed through the SAST score (17.4 ± 3.9 vs. 21.1 ± 5.7; <it>p </it>= 0.029).</p> <p>Conclusions</p> <p>The implementation of an electronic surveillance system was feasible so as to measure the burden of HZ and PHN within the rural general practice setting in Crete.</p